Add Marshal.PtrToStringUni internal implementation in S.P.CoreLib

This change adds and internal Marshal.PtrToStringUni in S.P.CoreLib to unblock  the benchmark Sergiy has been working on.

[tfs-changeset: 1662877]

1 files changed, 2 insertions, 18 deletions

diff --git a/src/System.Private.Interop/src/System/Runtime/InteropServices/Marshal.cs b/src/System.Private.Interop/src/System/Runtime/InteropServices/Marshal.cs
index c655d8450..6f0cdfa09 100644
--- a/src/System.Private.Interop/src/System/Runtime/InteropServices/Marshal.cs
+++ b/src/System.Private.Interop/src/System/Runtime/InteropServices/Marshal.cs
@@ -99,28 +99,12 @@ namespace System.Runtime.InteropServices
 
         public static unsafe String PtrToStringUni(IntPtr ptr, int len)
         {
-            if (ptr == IntPtr.Zero)
-                throw new ArgumentNullException(nameof(ptr));
-            if (len < 0)
-                throw new ArgumentException(nameof(len));
-
-            return new String((char*)ptr, 0, len);
+            return PInvokeMarshal.PtrToStringUni(ptr, len);
         }
 
         public static unsafe String PtrToStringUni(IntPtr ptr)
         {
-            if (IntPtr.Zero == ptr)
-            {
-                return null;
-            }
-            else if (IsWin32Atom(ptr))
-            {
-                return null;
-            }
-            else
-            {
-                return new String((char*)ptr);
-            }
+            return PInvokeMarshal.PtrToStringUni(ptr);
         }
 
         public static String PtrToStringAuto(IntPtr ptr, int len)